Area Forecast Discussion
Issued by NWS Burlington, VT

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000 FXUS61 KBTV 231430 AFDBTV Area Forecast Discussion National Weather Service Burlington VT 1030 AM EDT Fri Jun 23 2017 .SYNOPSIS... Showers and thunderstorms will move through the area today. Locally heavy rainfall is possible with stronger showers and storms. A cold front will move through the region tonight, reducing the humidity and bringing a brief return to dry weather on Saturday. More showers return early next week. Temperatures will be near to a bit below their seasonal normals, with highs in the 70s to low 80s and lows in the 50s and low 60s. && .NEAR TERM /THROUGH SATURDAY/... As of 1030 AM EDT Friday...Flash Flood Watch issued for the Adirondacks and portions of central/northern VT through 1100 pm. MRMS estimates fairly accurate this morning showing a swatch of 0.75 to 2 inch rainfall along and 30 either side of a line from Edwards, NY through Saranac Lake, Burlington and St. Johnsbury. This has saturated soils in this area and with additional showers/scattered storms with heavy downpours in existing 1.7-1.9 PWAT airmass the potential for flash flooding in the watch area has increased (see hydro disc below for further details). Otherwise, did opt to lower maximum temperatures slightly based off higher degree of clouds and most recent LAMP output. Rest of forecast remains in good shape. Have a good day. Previous discussion...Warm front analyzed running east-west from southern shore of Lake Ontario and across southern Vermont. Area of showers and thunderstorms along and to the north of the front, aided by area of 500mb PVA moving into the region in west-southwest flow out of deepening trough to the west. Main body of rainfall will lift north this morning through 12z following track of the vort center and on nose of low level southwest jet of 30-40 knots. Expecting a lull after precip lifts north, then daytime destabilization will renew chances for convection through the day. With upper trough to west, and warm front and shortwave trough moving north there isn`t organized forcing thinking is that showers and thunderstorms will have to be all instability driven. Thermodynamic profile continues to show very efficient rainfall processes, with pwats near 2 inches, warm cloud depth over 12K feet, and a tall skinny CAPE. Given southwest unidirectional flow there is the potential for storms to train over the same location and produce heavy rainfall rates. Severe threat less straightforward, with parameters pointing toward marginal risk from SPC. Best 0-6km shear of 40-50 kts lifts north this morning with the warm front and low level jet, then settles down to 35-40 kts for the afternoon storms. Likewise CAPE is a modest 1500 j/kg based on max surface temp in the low 80s. Kept gusty winds/small hail in forecast, but feel the biggest threat today is heavy rainfall. For tonight a cold front moves northwest to southeast bringing rain chances to an end from west to east. Saturday will be mostly dry, however a chance for showers remains mainly in the northern higher terrain with passage of a shortwave trough in southwest flow as trough to the west deepens. Lows tonight still in the 60s, then cooler air trickles in for Saturday with highs in the 70s. && .SHORT TERM /SATURDAY NIGHT THROUGH SUNDAY/... As of 430 AM EDT Friday...Any showers Saturday evening should end before midnight as any convection will mainly be instability driven. Dry weather is then expected during the overnight hours Saturday night through much of the morning hours on Sunday. Shortwave trough will move across the area Sunday afternoon and enhance the potential for showers...especially over the northern half of the area. Lows Saturday night will be in the 50s to around 60 with highs on Sunday in the 70s. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... As of 430 AM EDT Friday...Area remains under a broad upper level trough of low pressure through about midweek. Shortwave troughs moving through the large scale trough along with daytime heating to destabilize the atmosphere will be enough to keep a chance of showers going just about every day of the first half of the week. The pattern will change as upper trough moves east by Thursday and upper ridging builds in. Looking at drier weather for the Thursday/Friday time period along with a drying trend. && .AVIATION /14Z FRIDAY THROUGH TUESDAY/... Through 12Z Saturday...Rain creating mvfr to ifr conditions for most TAF terminals, except KRUT far enough south to be on the fringe. As the rain area lifts slowly north through late morning conditions to improve to vfr cigs. After the morning rain kept vcsh for the rest of the day. Uncertainty remains for forcing of afternoon convection, and until we`re able to pinpoint locations as storms fire VCSH will suffice. Cigs drop to IFR after 00z with passage of cold front. South winds with gusts in the high teens today turn southwest and west overnight with passage of front. Outlook... Saturday: VFR. Slight Chance SHRA...Slight Chance TSRA. Saturday Night: VFR. NO SIG WX. Sunday: VFR. Breezy. Chance SHRA. Sunday Night: VFR. Breezy. Chance SHRA. Monday: VFR. Chance SHRA. Monday Night: VFR. Chance SHRA. Tuesday: VFR. Chance SHRA. && .HYDROLOGY... As of 1030 AM EDT Friday...Storms will have high rainfall rates today, and training storms moving over same location could produce areas of flash flooding in the Flash Flood Watch area, where 0.75 to locally 2 inches of precipitation fell earlier today. With the overnight rains, 1 hour FFG has decreased into the 1.0 to 1.5 inch range, with 3-hourly guidance running from 1.5 to around 2 inches. With lack of organized forcing mechanism for storms this afternoon heavy rainfall will be hit or miss, but latest output suggests instability on the south side of warm front to our immediate north may drive additional activity into the watch area. Per coordination with NERFC additional amounts of 1 to 2 inches is forecast, which raises concerns for smaller watersheds. Larger rivers and will see modest rises but should remain within banks. && .BTV WATCHES/WARNINGS/ADVISORIES... VT...Flash Flood Watch through this evening for VTZ005>010-017-018. NY...Flash Flood Watch through this evening for NYZ028>031-034-035. && $$ SYNOPSIS...Hanson NEAR TERM...JMG/Hanson SHORT TERM...Evenson LONG TERM...Evenson/Taber AVIATION...Hanson HYDROLOGY...JMG/Hanson

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